Quality control, one of the most important concepts in modern industry, has been a challenging and crucial topic for nearly all of the companies that have been existed to serve goods/services. By the definition, quality is considered as “fitness to the application and fulfilling the customer expectation”. It means that it is all about expectations and suitability. The notion of quality solely depends on perception. One may not consider a service high quality whereas the satisfaction of another customer is fulfilled. In most cases, the existence of an industrial organization hugely relies on the quality of their service. It is a major concern for every company that is willing to survive in the market for a long period of time. The satisfaction of customers is the most important part of quality management. Therefore, nearly all of the corporative organizations have to have a department for quality control and management operations. Thanks to scientific studies, many different methods and systems were developed. This blog post will focus on quality assurance (QA) and quality control (QC) processes which fall under the topic of quality management. Seven tools of QC will be explained. But besides those, quality planning will be briefly mentioned. Several methods for quality improvement will also be presented within the content of this post.
Nothing gets done without a plan of action. Quality planning can be defined as the initial step of quality management where the development of products, systems, and processes are done in order to meet customer expectations. The planning step involves defining the customer profile and needs. Procedures and objectives are in this step.
An example of quality planning: A quality plan is simply a document that specifies the standards, applications, specs, and act of the plan in sequence. Let’s take a metal parts manufacturer for example. After the standards and specifications have been defined, a sequential inspection process (non-destructive, destructive tests, hands-on inspection, etc.) is created. This process makes sure that the fabricated part is satisfactory in terms of standards and specs. Parts that fail to complete the qualification process are sent to scrap or deburring. This planning operation may contain quality control and quality assurance plans.
Quality assurance and quality control steps form the core of a quality management system. These sets of processes combined help to ensure service/products and meet the expectations of the customer. These two terms are often used to mention ensuring the quality of a product, however, they are not the same concepts. Quality assurance is the prevention method of possible defects and problems before the production of goods and services. According to ISO 9000 standards, this operation is defined as a subcategory of the quality management process focused on the assurance that quality requirements will be met. This mechanism is prior to quality control, aiming to minimize defects and of course lots of time and effort. In essence, quality assurance makes the producer sure about the efforts and precautions are taken are on the right path for achieving the requested quality levels. Quality control, on the other hand, focuses on the detection of flaws in products. It ensures that created goods/services follow the standards and requirements of the design. Again, according to ISO 9000, it is defined as a part of quality management used to meet quality requirements. Quality control is a reactive process and it is done after quality assurance. This operation includes many operations within. If we are to give an example from metal fabrication, tensile testing is done for the fabricated metal parts to identify whether the product meets the requirements in terms of tensile strength.
In order to sum up the main difference between these two concepts, it can be concluded that the quality assurance process focuses on preventing while the quality control process aims to detect the flaw of created goods and services.
Seven Basic Tools of QC
Developed by the Japanese people, seven basic tools of quality control help industrial organizations solve complex challenges in quality. This methodology can be applied in any kind of industrial effort, thus widely used. These tools are:
Stratification, based on dividing the existing data into sub categories to derive meaningful information and understand the problem.
Histogram, basically distribute the data as bar graphs to see whether there exists an abnormality or not. By doing this, data may reveal the primal problematics clearly.
Check Sheet, also known as Tally Sheet, helps to see the occurrence pattern of the problem by marking checkpoints on the tabular form. In some cases, it might even show the causes of problems.
Cause-Effect Diagram (also known as Ishikawa or fishbone diagram), focuses on understanding the root cause of the problem. First, the problem is identified. Then a horizontal line is drawn where the other branches of possible roots of the defect (machinery, labor, material, measurements, environment, methods) are created. Possible reasons for each branch are written under (For instance, problems can be emerged from machinery due to lack of maintenance). This tool enables much more efficient brainstorming and is the most essential piece of QC.
Pareto Chart, used to point out the most crucial factors that cause the problem. Named after Vilfredo Pareto, it tells us that 80% of problems are caused by 20% of primary factors referred as Vital Few while the rest is called Trivial Many. This instrument helps to set Vital few and Trivial many apart.
Scatter Diagram, is used to check whether the data is positively or negatively correlated. All the data is scattered on an XY plot.
Control Chart, simply a statistical graph used to determine whether data obtained from the process is acceptable within upper and lower limits.
Quality Improvement and QI Methods
The development of quality management systems on the road to serving at higher precision levels by means of desired quality control standards has a direct correlation with quality improvement. Many engineers, scientists, and people from other branches have developed different approaches for quality improvement, all of which are tools for the refinement of processes. The most widely known methods are:
ISO 9004, performance improvement guidelines.
ISO 9001, quality management system. Organizations that are able to meet the demands of this standard can acquire ISO 9001 certification. This certification enables them to show that the quality of created goods/services accommodates worldwide known standards. It is the only certified standard.
Taguchi Methods, statistical methods named after Genichi Taguchi, an engineer and statistician. These methods mainly focus on quality improvement based on the minimization of the number of experiments needed for the prediction of the best results.
PDCA, plan, do, check, act cycle used for QC operations.
There exist numerous different methods, however many of them are specialized in certain working areas.